The opposite of "grew smaller" would be "grew larger". Simply put, when something grows smaller it decreases in size, whereas when it grows larger it increases in size. Other antonyms for "grew smaller" could include: expanded, increased, grew bigger, swelled, developed, and progressed. These words all convey a sense of growth and magnification, which can be used to describe various situations, from physical growth to the development of skills or relationships. Understanding antonyms is important when trying to convey a specific message or idea, as it allows for greater clarity and precision in language.